摘要

In this paper, a new way to construct differentially 4-uniform (n, n 1)-functions is presented. As APN (n, n)-functions, these functions offer the best resistance against differential cryptanalysis and they can be used as substitution boxes in block ciphers with a Feistel structure. Constructing such functions is assumed to be as difficult as constructing APN (n, n)-functions. A function in our family of functions can be viewed as the concatenation of two APN (n 1,n 1)-functions satisfying some necessary conditions. Then, we study the special case of this construction in which the two APN functions differ by an affine function. Within this construction, we propose a family in which one of the APN functions is a Gold function which gives the quadratic differentially 4-uniform (n, n 1)-x, x(n)) -> x(2i) (+ 1) + x(n)x where x is an element of F-2(n-1) and x(n) is an element of F-2 with gcd (i,n - 1) = 1. We study the nonlinearity of this function in the case i = 1 because in this case we can use results from Carlitz which are unknown in the general case. We also give the Walsh spectrum of this function and prove that it is CCZ-inequivalent to functions of the form L o F where L is an affine surjective (n, n 1)-function and F is a known APN (n, n)-function for n <= 8, or the Inverse APN (n, n)-function for every n >= 5 odd, or any AB (n, n)-function for every n > 3 odd, or any Gold APN (n, n)-function for every n > 4 even.

  • 出版日期2015-11